The 28-year-old took to Instagram and reposted a video uploaded by the account motivationaddictzz which included a a clip of NFL legend Deion Saunders, who is renowned for his motivational speeches.
The two-time Super Bowl champion said in the video, which was reposted by United's Fernandes: "Look at me. What about me would make you think I care about your opinion of me?
"Your opinion of me is not the opinion that I have of myself.
"You ain't make me so you can't break me. You didn't build so you can't kill me.
"You know what, God established me so ain't nothing you can do to me.
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"I been him. I been a difference maker, a game changer. I been that guy. So what would change?
"Not a darn thing. I am not even playing the game and you got an opinion of me.
"I love it but I don't care and I wish the world thought like that.
"Youngsters, if you're out there right now, do not give a darn what opinion people have of you, as long as that opinion is not consistent with of yourself. You be you."
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The clip appears to be in response to criticism over Fernandes' leadership at United.
The Portugal international took the armband this season with Harry Maguire relinquishing his duties as captain.
While it did not go down well with Maguire, many sections of fans were happy to see Fernandes given the role for good having largely taken on the responsibilities as the defender remained sidelined last season.
But not everyone has agreed with the move with some criticising Fernandes for his petulance and theatrics.
talkSPORT's Simon Jordan has been among those to take a swipe at the playmaker, saying the Portuguese isn't a leader.
In response to Fernandes demanding an apology from referees in the wake of United's 2-0 defeat to Tottenham, Jordan said earlier this week: "I don't think he is a leader. Clearly, he is not a leader.
"And why you would want him as a leader, I don't know. When you have leaders like that, you will get certain outcomes.
"If Manchester United's desire is to be top of the tree again, you are not going to get there with Bruno Fernandes as your captain."